Factors affecting production of coccoid forms by Campylobacter jejuni on solid media during incubation

Zoonotic and Public Health Implications of Campylobacter Species and Squamates (Lizards, Snakes and Amphisbaenians)

Campylobacter spp. is one of the most widespread infectious diseases of veterinary and public health significance. Globally, the incidence of campylobacteriosis has increased over the last decade in both developing and developed countries. Squamates (lizards, snakes and amphisbaenians) are a potential reservoir and source of transmission of campylobacteriosis to humans. This systematic review examined studies from the last 20 years that have reported squamate-associated human campylobacteriosis. It was found that C. fetus subsp. testudinum and C. fetus subsp. fetus were the most common species responsible for human campylobacteriosis from a squamate host. The common squamate hosts identified included bearded dragons (Pogona vitticeps), green iguana (Iguana iguana), western beaked gecko (Rhynchoedura ornate) and blotched blue-tongued skink (Tiliqua nigrolutea). People with underlying chronic illnesses, the immunocompromised and the elderly were identified as the most vulnerable population. Exposure to pet squamates, wild animals, consumption of reptilian cuisines and cross contamination with untreated water were risk factors associated with Campylobacter infections. Proper hand hygiene practices, responsible pet ownership, ‘One Health’ education and awareness on zoonotic diseases will help reduce the public health risks arising from Campylobacter exposure through squamates. Continued surveillance using molecular diagnostic methods will also enhance detection and response to squamate-linked campylobacteriosis.

The Campylobacter jejuni helical to coccoid transition involves changes to peptidoglycan and the ability to elicit an immune response

Campylobacter jejuni is a prevalent enteric pathogen that changes morphology from helical to coccoid under unfavorable conditions. Bacterial peptidoglycan maintains cell shape. As C. jejuni transformed from helical to coccoid, peptidoglycan dipeptides increased and tri- and tetrapeptides decreased. The DL-carboxypeptidase Pgp1 important for C. jejuni helical morphology and putative N-acetylmuramoyl-L-alanyl amidase AmiA were both involved in the coccoid transition. Mutants in pgp1 and amiA showed reduced coccoid formation, with ∆pgp1∆amiA producing minimal coccoids. Both ∆amiA and ∆amiA∆pgp1 lacked flagella and formed unseparated chains of cells consistent with a role for AmiA in cell separation. All strains accumulated peptidoglycan dipeptides over time, but only strains capable of becoming coccoid displayed tripeptide changes. C. jejuni helical shape and corresponding peptidoglycan structure are important for pathogenesis-related attributes. Concomitantly, changing to a coccoid morphology resulted in differences in pathogenic properties; coccoid C. jejuni were non-motile and non-infectious, with minimal adherence and invasion of epithelial cells and an inability to stimulate IL-8. Coccoid peptidoglycan exhibited reduced activation of innate immune receptors Nod1 and Nod2 versus helical peptidoglycan. C. jejuni also transitioned to coccoid within epithelial cells, so the inability of the immune system to detect coccoid C. jejuni may be significant in its pathogenesis.

Description of Campylobacter jejuni Bf, an atypical aero-tolerant strain

BACKGROUND

Campylobacter jejuni is a leading cause of bacterial enteritis worldwide. This microaerophilic bacterium can survive in aerobic environments, suggesting it has protective mechanisms against oxidative stress. The clinical C. jejuni Bf strain is characterized by an increased resistance to oxygen. This study aimed to characterize the behavior of the clinical C. jejuni Bf strain under an aerobic atmosphere and in response to ROS-promoter agents.

METHODS

Growth was studied in both aerobic and microaerobic conditions using classic cultivable methods. Electronic microscopy and mreB gene expression were used to evaluate the morphology of this strain under aerobic conditions. The survival under oxidative stress was tested in the presence of different concentrations of hydrogen peroxide (H2O2) and paraquat (PQ).

RESULTS

The results showed that C. jejuni Bf strain can grow aerobically, unlike other strains of C. jejuni tested. Cells of C. jejuni Bf exposed to oxidative stress presented changes in morphology and the gene mreB, responsible for maintaining the bacillary cell morphology, was down-expressed. In aerobically acclimated conditions, C. jejuni Bf exhibited a higher survival rate of 52 % in the presence of H2O2 (1 mM) compared to the reference strain NCTC 11168. Concentrations above 1 mM PQ were lethal for the reference strain but not for C. jejuni Bf.

CONCLUSIONS

Taken together, these data highlight the resistance to oxidative stress conditions of C. jejuni Bf, indicating that this microorganism seems more adapted to survival in hostile environmental conditions.

The acid adaptive tolerance response in Campylobacter jejuni induces a global response, as suggested by proteomics and microarrays

Campylobacter jejuni CI 120 is a natural isolate obtained during poultry processing and has the ability to induce an acid tolerance response (ATR) to acid + aerobic conditions in early stationary phase. Other strains tested they did not induce an ATR or they induced it in exponential phase. Campylobacter spp. do not contain the genes that encode the global stationary phase stress response mechanism. Therefore, the aim of this study was to identify genes that are involved in the C. jejuni CI 120 early stationary phase ATR, as it seems to be expressing a novel mechanism of stress tolerance. Two-dimensional gel electrophoresis was used to examine the expression profile of cytosolic proteins during the C. jejuni CI 120 adaptation to acid + aerobic stress and microarrays to determine the genes that participate in the ATR. The results indicate induction of a global response that activated a number of stress responses, including several genes encoding surface components and genes involved with iron uptake. The findings of this study provide new insights into stress tolerance of C. jejuni, contribute to a better knowledge of the physiology of this bacterium and highlight the diversity among different strains.

Three Tests Used to Identify Non-Culturable Form of Helicobacter pylori in Water Samples

Background:

Helicobacter pylori, causing the most common chronic bacterial infection, exist in two forms; bacilli and coccoid. The coccoid form is identified as viable but non-culturable bacteria.

Objectives:

The current study aimed to conduct culture, polymerase chain reaction (PCR), and loop-mediated isothermal amplification (LAMP) tests to identify coccoid forms of H. pylori.

Materials and Methods:

The PCR and LAMP tests were optimized using specific primers for glmM gene. The sensitivity and specificity of the tests were determined. The current experimental study was conducted on 10 different strains isolated from clinical cases (H1-H10). The isolates were added to tap water and incubated at three different temperatures for one and two months intervals. After pure-culturing of the bacteria, DNAs were extracted and PCR and LAMP were performed.

Results:

Ten copies of targeted DNA were required for PCR detection whereas only five copies gave a positive reaction by LAMP assay, with 100% specificity. Of the 10 isolates inoculated in water for one and two months at three different temperatures 4, 22, and 37°C, only three cases (5%) were found positive in the first month; 13 (21.6%) and 29 cases (48.3%) were also positive by PCR and LAMP tests in the first and second months.

Conclusions:

Results of the current study confirmed that molecular methods such as PCR and LAMP were much more sensitive, rapid, and specific than culturing to identify non-culturable coccoid forms of H. pylori in water.

Role of environmental survival in transmission of Campylobacter jejuni

Campylobacter species are the most common cause of bacterial gastroenteritis, with C. jejuni responsible for the majority of these cases. Although it is clear that livestock, and particularly poultry, are the most common source, it is likely that the natural environment (soil and water) plays a key role in transmission, either directly to humans or indirectly via farm animals. It has been shown using multilocus sequence typing that some clonal complexes (such as ST-45) are more frequently isolated from environmental sources such as water, suggesting that strains vary in their ability to survive in the environment. Although C. jejuni are fastidious microaerophiles generally unable to grow in atmospheric levels of oxygen, C. jejuni can adapt to survival in the environment, exhibiting aerotolerance and starvation survival. Biofilm formation, the viable but nonculturable state, and interactions with other microorganisms can all contribute to survival outside the host. By exploiting high-throughput technologies such as genome sequencing and RNA Seq, we are well placed to decipher the mechanisms underlying the variations in survival between strains in environments such as soil and water and to better understand the role of environmental persistence in the transmission of C. jejuni directly or indirectly to humans.

Campylobacter epidemiology: an aquatic perspective

Members of the genus Campylobacter have established themselves as the most common human gastro-enteric pathogens throughout much of the developed world. The ubiquitous distribution of Campylobacter spp. in animal reservoirs and food products derived thereof make such vehicles primary risk factors in contracting campylobacteriosis. The contamination rates, identification of common pathogenic serotypes and extended survival of Campylobacter in surface waters illustrates the potential, but yet to be quantified, campylobacteriosis risk associated with untreated water. The existence and potential pathogenicity of viable but nonculturable forms of Campylobacter remains a contentious subject. Furthermore, the role of such forms in the epidemiology of Campylobacter related disease and their involvement in the large number of waterborne gastroenteritis outbreaks from which a disease agent cannot be isolated remains to be fully clarified. This article presents a survey of current perspectives with regard to the survival and epidemiology of Campylobacter spp. in natural water systems.

The Dienes phenomenon: competition and territoriality in Swarming Proteus mirabilis

When two different strains of swarming Proteus mirabilis encounter one another on an agar plate, swarming ceases and a visible line of demarcation forms. This boundary region is known as the Dienes line and is associated with the formation of rounded cells. While the Dienes line appears to be the product of distinction between self and nonself, many aspects of its formation and function are unclear. In this work, we studied Dienes line formation using clinical isolates labeled with fluorescent proteins. We show that round cells in the Dienes line originate exclusively from one of the swarms involved and that these round cells have decreased viability. In this sense one of the swarms involved is dominant over the other. Close cell proximity is required for Dienes line formation, and when strains initiate swarming in close proximity, the dominant Dienes type has a significant competitive advantage. When one strain is killed by UV irradiation, a Dienes line does not form. Killing of the dominant strain limits the induction of round cells. We suggest that both strains are actively involved in boundary formation and that round cell formation is the result of a short-range killing mechanism that mediates a competitive advantage, an advantage highly specific to the swarming state. Dienes line formation has implications for the physiology of swarming and social recognition in bacteria.

Environmental stress factors affecting survival and virulence of Campylobacter jejuni

Enteric pathogens are constantly exposed to stressful conditions in their natural habitat in the host and even more in the extra-host environment, including food processing. The aim of this study was to evaluate the effect of selected environmental stress factors: temperature shift, starvation and atmospheric oxygen concentration on culturability/viability of two Campylobacter jejuni isolates. Additionally, after stress exposure, in an in vitro cell culture model using Caco-2 cells, the adhesion, invasion and intracellular survival of C. jejuni were studied. Nutrient insufficiency was the most powerful stress factor which significantly affected C. jejuni culturability and viability, as well as, adhesion and invasion properties. Temperature elevation induced a transient growth arrest, and temporary loss of pathogenic potential as indicated by impaired adhesion and invasion efficiency of C. jejuni. However, bacteria recovered within 24-48h inside the Caco-2 cells. Oxidative stress neither affected C. jejuni growth nor reduced the binding and invasion into Caco-2 cells. Only 5h oxygen exposure increased the invasion capability and intraepithelial survival of the clinical isolate. Modulation of C. jejuni virulence in response to environmental stress factors may have further implications in the pathogenesis of campylobacteriosis.

Environmental survival mechanisms of the foodborne pathogen Campylobacter jejuni

Campylobacter spp. continue to be the greatest cause of bacterial gastrointestinal infections in humans worldwide. They encounter many stresses in the host intestinal tract, on foods and in the environment. However, in common with other enteric bacteria, they have developed survival mechanisms to overcome these stresses. Many of the survival mechanisms used by Campylobacter spp. differ from those used by other bacteria, such as Escherichia coli and Salmonella spp. This review summarizes the mechanisms by which Campylobacter spp. adapt to stress conditions and thereby increase their ability to survive on food and in the environment.

Temperature-Dependent Genome Degradation in the Coccoid Form of Campylobacter jejuni

Campylobacter jejuni undergoes a dramatic morphological transformation from a corkscrew-shaped rod to a coccoid form in response to unfavorable conditions. It has been speculated that the coccoid plays an important role in the survival and dissemination of C. jejuni but questions still remain regarding the viability of coccoid cells. Characterization of the genome of coccoid cells found that newly formed coccoid cells (i.e., 1-3 days) had a SmaI-digestion profile identical to that of spiral-shaped cells; however, there was a progressive degradation of the DNA with continued incubation at 37 degrees C. Concomitant with genome degradation was the detection of DNA in supernatants of coccoid cells. In contrast, cells incubated at 4 degrees C retained a spiral shape and their SmaI-digestion profile for 8 weeks and released little DNA into the medium. Thus, low temperature inhibited both coccoid formation and genome degradation. Collectively, these data support the theory that the coccoid form of C. jejuni is a manifestation of cellular degradation and spiral-shaped cells, or possibly coccoid cells formed at low temperature, are the most probable candidates for a viable but nonculturable form of this pathogen.

Identification of a novel stress resistance mechanism in Campylobacter jejuni

AIM

To study stress resistance mechanisms in Campylobacter spp.

METHODS AND RESULTS

Campylobacter strains were grown to the appropriate phase in Brucella broth. The cells were diluted into either cell-free spent medium (obtained by filtration of a grown culture) or a freshly prepared medium and the pH reduced to 4.5, a lethal pH value. At suitable time intervals survivors were enumerated on Campylobacter blood free selective agar base. The cell-free spent medium from mid-exponential and stationary phase had a protective effect on acid and thermal stress in Campylobacter jejuni CI 120, a natural isolate. The protective effect of the extracellular compound was not significantly inactivated by boiling, but was inactivated by proteinase.

CONCLUSIONS

The present study suggests that a protein (or proteins) accumulated by C. jejuni CI 120 during growth may play an active role in the induction of stress responses and that this protein is heat stable.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results indicate that C. jejuni CI 120, a natural isolate, has the ability to use extracellular signalling mechanisms to induce tolerance to stress factors. This is a major advancement in the understanding of the physiological basis for survival of C. jejuni in the environment.

Induction of an adaptive tolerance response in the foodborne pathogen, Campylobacter jejuni

In this study we aimed to determine if Campylobacter had the ability to induce an adaptive tolerance response (ATR) to acid and/or aerobic conditions. Campylobacter jejuni CI 120 was grown to the appropriate phase in Brucella broth under microaerobic conditions. Cells were initially adapted to a mild stress (pH 5.5) for 5 h prior to challenge at pH 4.5, a lethal pH. Survival was examined by determining the numbers of viable cells on Campylobacter blood free selective agar base. Stationary phase cells adapted at pH 5.5 induced an ATR that enabled a 100-fold greater survival compared to an uninduced culture. Aerobic adaptation also protected the cells against acid challenge. The cross protection provided a 500-fold increase in survival when compared to unadapted cells. The incorporation of chloramphenicol during the induction period eliminated the ATR and resulted in death kinetics similar to an uninduced culture. These data suggest that Campylobacter spp. have the ability to induce an ATR to sublethal treatments, which increased their ability to withstand subsequent stresses.

Survival of Campylobacter jejuni in biofilms isolated from chicken houses

Campylobacter jejuni is a thermophilic and microaerophilic enteric pathogen associated with poultry. Biofilms may be a source of C. jejuni in poultry house water systems since they can protect constituent microorganisms from environmental stress. In this study, the viability of C. jejuni in biofilms of gram-positive chicken house isolates (P1, Y1, and W1) and a Pseudomonas sp. was determined using a cultural method (modified brucella agar) and direct viable count (DVC). Two-day biofilms grown on polyvinyl chloride (PVC) coupons in R2A broth at 12 and 23 degrees C were incubated with C. jejuni for a 6-h attachment period. Media were then refreshed every 24 h for 7 days to allow biofilm growth. Two-day biofilms of P1, Y1, and Pseudomonas spp. enhanced attachment (P < 0.01) of C. jejuni (4.74, 4.62, and 4.78 log cells/cm2, respectively) compared to W1 and controls without preexisting biofilm (4.31 and 4.22 log cells/cm2, respectively). On day 7, isolates P1 and Y1 and Pseudomonas biofilms covered 5.4, 7.0, and 21.5% of the surface, respectively, compared to 4.9% by W1. Viable C. jejuni on the surface decreased (P < 0.05) with time, with the greatest reduction occurring on surfaces without a preexisting biofilm. The number of viable C. jejuni determined by DVC was greater than that determined by the cultural method, indicating that C. jejuni may form a viable but nonculturable state within the biofilm. Both DVC and the cultural method indicate that biofilms enhance (P < 0.01) the survival of C. jejuni during incubation at 12 and 23 degrees C over a 7-day period.

Culturability, injury and morphological dynamics of thermophilic Campylobacter spp. within a laboratory-based aquatic model system

AIMS

To study the survival processes of thermophilic Campylobacter spp. within a modelled aquatic system and particularly the involvement and survival potential of viable but non-culturable forms.

METHODS AND RESULTS

The survival and morphological characteristics of populations of thermophilic Campylobacter species exposed to simulated aquatic conditions were examined using a combination of cultural and microscopic techniques. Populations underwent progressive decay when exposed to simulated aquatic conditions. The rates of population decay were observed to be significantly greater at the higher temperature (20 degrees C) with a rapid transition of the dominant sub-populations from non-stressed to dead cells occurred within 3 days. At 10 degrees C the rate of culturability loss was much reduced with substantial development (approx. 80% of total population) of viable but non-culturable (VBNC) populations by all species within 3 days, declining to represent approximately 5-25% of the total population at day 60. Significant differences (P < 0.001) were identified between decay rates as a consequence of different species, sub-populations and temperature but not between sub-populations of different species. Morphological variants including spiral, elongated spirals and rods, short rods and coccoid forms were identified. The endpoints of morphological transition were temperature-independent and isolate-specific yet the rate of morphological transition was directly related to temperature and approximately equivalent between species.

CONCLUSION

The VBNC state is a transitory stage in the degeneration of Campylobacter population within the aquatic environments simulated during this study.

SIGNIFICANCE AND IMPACT OF THE STUDY

VBNC cells form the most persistent, viable, potentially pathogenic sub-population of Campylobacter populations exposed to aquatic stress conditions.

The physiology of Campylobacter species and its relevance to their role as foodborne pathogens

Campylobacter jejuni and C. coli are recognised as the leading causes of bacterial foodborne diarrhoeal disease throughout the development world. While most foodborne bacterial pathogens are considered to be relatively robust organisms, as a consequence of the necessity to survive the inimical conditions imposed by food processing and preservation, Campylobacter species have uniquely fastidious growth requirements and an unusual sensitivity to environmental stress. Campylobacters also lack many of the well characterised adaptive responses that can be collated with resistance to stress in other bacteria. The aim of this review is to outline the unusual physiology of campylobacters (C. jejuni and C. coli) and to describe how this influences their role as foodborne pathogens.

Electron microscopic evaluation of adhesion of Helicobacter pylori to the gastric epithelial cells in chronic gastritis

BACKGROUND

The adhesion of H. pylori to the gastric epithelial cells may be an essential step for the pathophysiology of various H. pylori-induced gastrointestinal diseases. The purpose of this study was to investigate the ultrastructural relation of H. pylori and gastric epithelial cells in their adhesion.

METHODS

Endoscopic biopsy of gastric antrum and body was performed from 15 patients (9 men, 6 women) with chronic gastritis and H. pylori infection. The specimens were processed for electron microscopy and observed with a transmission electron microscope (Hitachi H-600).

RESULTS

On the basis of morphological appearances, the adhesions of H. pylori to the gastric epithelial cells were categorized into three types; filamentous connection, adhesion pedestals and membrane fusion. Coccoid and undetermined forms adhered mainly by the filamentous connection, whereas the bacillary forms adhered primarily by the adhesion pedestals and membrane fusion.

CONCLUSION

Various types of adhesion were associated with H. pylori and gastric epithelium. Further studies are needed to evaluate the influence of different types of adhesion to the pathophysiology of H. pylori.

Influence of activated charcoal, porcine gastric mucin and beta-cyclodextrin on the morphology and growth of intestinal and gastric Helicobacter spp

Bile-tolerant Helicobacter spp. are emerging human and animal pathogens. However, due to their fastidious nature, which requires nutrient-rich complex media to grow, infection with these bacteria may be underestimated. The accumulation of toxic metabolites in cultures may be one of the main obstacles for successful culture of these organisms. The present study examined various potential growth-enhancing substances for Helicobacter spp. and, furthermore, how they may affect spiral to coccoid conversion. Five Helicobacter spp. were cultured on agar and in broth media supplemented with activated charcoal, beta-cyclodextrin, or porcine gastric mucin. Growth was determined by estimating the numbers of colony-forming units and colony diameter, as well as bacterial cell mass. Coccoid transformation was estimated every 24 h by both Gram and acridine-orange staining. Activated charcoal was superior in supporting growth and increased cell mass on agar and in broth media. beta-Cyclodextrin delayed spiral to coccoid conversion by Helicobacter pylori and Helicobacter canis, whereas activated charcoal delayed the conversion to coccoid forms of Helicobacter hepaticus and Helicobacter bilis. The progression to coccoid forms by Helicobacter pullorum on agar media was not influenced by any growth supplement. The spiral to coccoid conversion was more rapid in broth media than on agar media. The growth enhancement observed is probably related to the capacity of activated charcoal to remove toxic compounds in culture media.

Helicobacter pylori: cultivability and antibiotic susceptibility of coccoid forms

Helicobacter pylori is an actively dividing helical bacterium that changes to coccoid morphology as the culture ages. It has been suggested that the coccoid forms may be involved in transmission of infection and in relapses following antimicrobial therapy. The aim of this investigation was to determine the survival and susceptibility of the coccoid forms to amoxycillin, erythromycin, gentamicin and metronidazole. Colony counts and microscopic examination were performed after 1-4 weeks of culture. At 2 and 4 weeks, identical cultures were treated with the antibiotics for 24 h. Our results showed that 4-week cultures of coccoid forms were cultivable after antibiotic treatment.

Morphological changes of synchronized Campylobacter jejuni populations during growth in single phase liquid culture

Campylobacter jejuni strains demonstrate a variety of growth phase-linked distinct morphological forms when grown in liquid culture. The typical spiral form of the organism, evident during logarithmic phase, undergoes elongation during stationary phase before becoming coccoid via the formation of membrane blebs and budded forms in decline phase. Cellular elongation and coccoid formation occurred despite the inhibition of protein synthesis and without a detectable change in the protein components of the inner and outer cell membranes.

Changes in the evolution of the antigenic profiles and morphology during coccoid conversion of Helicobacter pylori

OBJECTIVES

The significance of the coccoid forms of H. pylori is still controversial and the questions of whether these forms are viable and infective or degenerative are still open. We induced conversion from rod to coccoid forms and studied morphological changes and antigenic evolutions during this conversion and, thereby, elucidated the viability of coccoid forms.

METHODS

The H. pylori strain (C001) used for Western blotting was isolated from the patient with gastric cancer. The antigenic evolution during coccoid conversion of H. pylori was studied by Western blotting, using different sera from thirty patients known to be culture positive. These sera were used to reveal the total antigens of the strain cultured for 2 days (100% rod) and 15 days (> 99% coccoid). After SDS-PAGE, with 10% separating gel of total antigens (rod and coccoid), transblotting (Trans-Blot electrophoretic cell, Bio-Rad) was taken onto a nitrocellulose membrane (Bio-Rad). Then, the blots, with human sera diluted at 1/100, were developed with color reaction by goat serum anti-human IgG with alkaline phosphatase and BCIP.

RESULTS

The antigenic profiles were not changed in 46.7% (14/30 cases) and were changed in 53.3% (16/30 cases) during coccoid conversion. Antigenic fractions changed during coccoid conversion were protein band at 120 kDa and band at 35 kDa, and were not detected in coccus forms. The rest of the profiles were identical between rod and coccoid forms. The protein which disappeared include CagA (120 kDa) and porin, or adhesin (35 kDa). The morphological changes during coccoid conversion were U shaped at day 7, doughnut shaped at day 9 and full coccoid at day 15.

CONCLUSIONS

The results showed that coccoid forms of H. pylori retain cellular structures similar to rod form, and some of the antigens (CagA and porin) disappeared during coccoid conversion. Therefore, coccoid form might be viable and represent one of the stages of H. pylori biological cycle.

Effect of low-osmolality nutrient media on growth and culturability of Campylobacter species

The growth and culturability of Campylobacter jejuni NCTC 11351 and other campylobacters were examined in media having different osmolalities at a range of temperatures (4, 25, and 42 degreesC). The medium osmolalities used ranged from the osmolality of full-strength nutrient medium (modified campylobacter broth having an osmolality of around 254 mosmol) down to 96 mosmol. The following two methods were used to produce media having different osmolalities: dilution of the nutrient medium with distilled water and reformulation of the medium such that the concentrations of various osmolytes were altered while the nutrient content of the medium was unchanged. The results obtained with the two experimental methods were similar, indicating that there was an osmotic threshold effect, such that none of the campylobacters examined (C. jejuni NCTC 11351 and ATCC 33291, Campylobacter lari, and Campylobacter coli) grew in media having osmolalities around 130 mosmol and at temperatures below at 42 degreesC. Conversely, growth occurred in media having osmolalities of around 175 mosmol and above. Osmolar concentrations can be expressed in terms of osmolarity or osmolality. Osmolality is easier to evaluate, is the more commonly used term, and was used in the current study. In nutrient media having low osmolalities (i.e., 130 mosmol and below), the number of CFUs per milliliter declined rapidly regardless of the temperature, and no cells were recovered after 24 h. However, at nongrowth temperatures (25 and 4 degreesC) in higher-osmolality media (175 mosmol and above) a significant population was recovered throughout the experiment (up to 96 h). In low-osmolality nutrient media, the cellular morphology was principally coccoid, while in the early stages of growth in full-strength media the morphology was predominantly rodlike. We propose that the formation of coccoid cells in these experiments was the result of osmotic stress in low-osmolality media. This osmotic effect was apparent regardless of the osmolyte used to reformulate the medium (NaCl, KCl, Na2SO4, NH4Cl, and glucose were used).

Coccoid forms of Helicobacter pylori are the morphologic manifestation of cell death

Helicobacter pylori can transform from its normal helical bacillary morphology to a coccoid morphology. Since this coccoid form cannot be cultured in vitro, it has been speculated that it is a dormant form potentially involved in the transmission of H. pylori and in a patient's relapse after antibiotic therapy. In this study we determined the effects of aging, temperature, aerobiosis, starvation, and antibiotics on the morphologic conversion rate and culturability of H. pylori. Aerobiosis and the addition of a bactericidal antibiotic to the culture medium resulted in the highest conversion rate. During the conversion to coccoid forms, the cultures always lost culturability at the stage where 50% of the organisms were still in bacillary form; this result indicated that culturability and coccoid morphology are two separate but related entities. Independent of the conditions used to induce the conversion into coccoids, the morphological conversion was accompanied by several marked antigenic and ultrastructural changes. Also, both the total amounts and the integrity of RNA and DNA were significantly reduced in coccoid forms. With the potential-sensitive probe diOC(5)-3, a clear loss of membrane potential in coccoid forms was observed. Inhibition of protein or RNA synthesis by the addition of bacteriostatic antibiotics did not prevent the conversion to coccoid forms but resulted in an increased conversion rate. Hence, we conclude that conversion of H. pylori from the bacillary to the coccoid form is a passive process that does not require protein synthesis. Our data suggest that the coccoid form of H. pylori is the morphologic manifestation of bacterial cell death.

Comparison of the nucleic acids of helical and coccoid forms of Helicobacter pylori

The nucleic acids of the helical and coccoid forms of Helicobacter pylori were studied to determine if the coccoid forms are "viable (capable of growing) but nonculturable." Using a reference strain (NCTC 11638) and five clinical strains, the nucleic acid contents, DNA integrity, and results of PCR and reverse transcription-PCR (RT-PCR) were compared for helical H. pylori and coccoid forms induced using glycochenodeoxycholic acid or bismuth citrate. The DNA and RNA contents of the coccoid forms were respectively 6.8- and 8.1-fold lower than those of helical H. pylori after 3 days of induction and 11.5- and 14.7-fold lower after 7 days. Agarose gel electrophoresis of DNA extracted from the coccoid forms after 3 days of induction showed a smear pattern indicating DNA cleavage, whereas DNA from helical H. pylori showed a single band with a high molecular mass. After 12 days of induction, all RNA samples from 100% coccoid cultures were negative for the mRNA of urease A or the 26-kDa species-specific protein by RT-PCR. However, most RNA samples obtained after 3 or 7 days of induction were positive at low levels despite the lack of recovery from these cultures. These results suggest that the coccoid form of H. pylori has impaired genomic DNA and is in the process of cellular degeneration, thus being still alive but nonincreasable.

Resuscitation of 'non-culturable' cells from aged cultures of Campylobacter jejuni

When stationary phase batch cultures of Campylobacter jejuni were stored in sealed flasks under static conditions, viable numbers declined from 2 x 10(9) c.f.u. ml-1 to around 10(3)-10(6) c.f.u. ml-1 within 4-6 weeks. When the aged cultures were sparged with a microaerobic gas mixture, there was a rapid increase in viable numbers accompanied by a change from predominantly coccoid to vibrioid morphology. The most probable number (MPN) technique was used to distinguish resuscitation of injured or dormant cells from multiplication of residual viable cells. MPN estimates using fresh Brucella broth containing 0.2% mucin revealed that plate counts underestimated the true viable count by up to 23-fold. The experiments clearly demonstrated that a proportion of surviving cells in aged cultures were in an injured or latent state that prevented growth on agar plates. It is possible that the size of this fraction is greater than was demonstrated and that much higher recoveries would be obtained under other recovery conditions. Nevertheless, from presently available evidence, it must be concluded that the size of the latent fraction is quite small and that most of the increase in count that occurs on regassing a spent culture comes from multiplication of residual viable cells.

Changes with growth rate in the membrane lipid composition of and amino acid utilization by continuous cultures of Campylobacter jejuni

Methods and media (defined and complex) are described which permit studies designed to determine the influence of single environmental factors on the survival and virulence of Campylobacter jejuni. The effect of growth rate on selected physiological traits (amino acid utilization, membrane lipid composition, motility, cell morphology) was studied in continuous culture. In both media, growth was at the expense of amino acid (serine, aspartate, glutamate and proline) catabolism. Slow growth in the complex medium shifted amino acid utilization from more (serine and aspartate) to less preferred substrates (glutamate, proline and possibly amino acids from the proteolysis of peptones). Low growth rates promoted the conversion of unsaturated 11-octadecenoic acid substituted phosphatidyl ethanolamines to corresponding 11-methylene substituted species, a feature correlated with stationary phase and exposure to environmental stress in other organisms. During continuous growth, cells lost motility although they still possessed flagella. Slow growth resulted in longer cells. Future studies will investigate the independent effects of nutrient stress and growth rate on the virulence and persistence of cells.

Changes in Helicobacter pylori ultrastructure and antigens during conversion from the bacillary to the coccoid form

In vitro, Helicobacter pylori converts from a bacillary to a full coccoid form via an intermediate U-shaped form. Organisms with a full coccoid form keep a double membrane system, a polar membrane, and invagination structures. Western blots (immunoblots) of sera from colonized patients show that some high-molecular-mass antigenic fractions are expressed only in coccoids. Conversely, fractions of 30 and 94 kDa were more intensively detected in the bacillary forms. These results suggest that (i) coccoid conversion is not a degenerative transformation and (ii) antigens specific to the coccoid forms are expressed in vivo.

DNA fingerprinting and serotyping of Campylobacter jejuni isolates from epidemic outbreaks

The aim of the present investigation was to compare DNA fingerprinting and serotyping (heat-stabile and heat-labile antigens) of isolates from epidemic outbreaks as well as of solitary isolates. Campylobacter jejuni isolates from two epidemic outbreaks in Sweden, one milkborne (35 isolates) and one waterborne (17 isolates), and one waterborne outbreak in Norway (11 isolates), as well as 30 solitary isolates from Swedish patients with gastroenteritis, were analyzed. A total of 93 isolates were analyzed. In the waterborne outbreak in Norway, only one serotype with one DNA pattern was found. In the milkborne outbreak in Sweden, two serotypes (HS2:HL4 and HSNT:HL4) with two different DNA patterns were found. The isolates from the waterborne outbreak in Sweden were different serotypes. For two isolates of the same serotype, different DNA patterns were seen. This was also recorded for isolates from solitary cases. It was concluded that serotyping is a useful tool in most epidemiological situations but sometimes lacks sufficient discriminatory power. DNA fingerprinting can add valuable epidemiological information to that supplied by serotyping and can in some situations provide sufficient epidemiological information when used alone.

Morphologic conversion of Helicobacter pylori from bacillary to coccoid form

The morphologic conversion of Helicobacter pylori from bacillary to coccoid form was studied by microscopy, viable count on agar plates, and bioluminescence assay of bacterial ATP. When morphologic conversion from bacillary to coccoid form was detected by microscopy, the viable counts and the bacterial ATP decreased. No viable count was found after nine days of incubation, but bacterial ATP was still present. In these cultures in which only the coccoid form of Helicobacter pylori was present, there was no accumulation of extracellular ATP, indicating no leaky cells. During the transition phase from the bacillary to the coccoid form of Helicobacter pylori, the addition of fresh medium increased the intracellular ATP 26-fold. The coccoid form of Helicobacter pylori had a 1000-fold lower ATP level per cell compared to the bacillary form, which indicates a decreased metabolic activity in the coccoid form. Addition of fresh medium to the coccoid cultures from days 9 and 10 increased the ATP level twofold. However, no conversion from coccoid to bacillary form was found in these cultures during prolonged incubation in fresh broth for four weeks. Such conversion needs to be demonstrated before it is proven that the coccoid form of Helicobacter pylori is responsible for transmission and relapse of infection.

Temperature-dependent membrane fatty acid and cell physiology changes in coccoid forms of Campylobacter jejuni

The effect of temperature and the availability of nutrients on the transition of spiral Campylobacter jejuni cells to coccoid forms was investigated. Ageing of spiral C. jejuni cells in either nutrient-poor or nutrient-rich environments resulted in the formation of nonculturable coccoid cells at 4, 12, and 25 degrees C after different periods, with the cells incubated at 4 degrees C in nutrient-deficient media remaining culturable the longest. To study the phenomenon, ATP levels, protein profiles, and fatty acid compositions were monitored under conditions where the transition from spiral to coccoid cells occurred. During storage, the levels of intracellular ATP were highest in cells incubated at low temperatures (4 and 12 degrees C) and remained constant after a small initial decrease. During the transformation from spiral to coccoid forms, no alteration in protein profiles could be detected; indeed, inhibition of protein synthesis by chloramphenicol did not influence the transition. Furthermore, DNA damage by gamma irradiation had no effect on the process. Membrane fatty acid composition of cocci formed at low temperatures was found to be almost identical to that of spiral cells, whereas that of cocci formed at 25 degrees C was clearly different. Combining these results, it is concluded that the formation of cocci is not an active process. However, distinctions between cocci formed at different temperatures were observed. Cocci formed at 4 degrees C show characteristics comparable to those of spirals, and these cocci may well play a role in the contamination cycle of C. jejuni.(ABSTRACT TRUNCATED AT 250 WORDS)

Morphological transformation of Helicobacter pylori during prolonged incubation: association with decreased acid resistance

The survival of clinical isolates of H pylori at two cultural ages (two and four days) at pH 2, in the presence of different buffers, with and without urea, was investigated. It was found that the morphological changes which occur with longer incubation of H pylori have an inverse correlation with its resistance to an acidic environment. The finding that the addition of urea almost reversed this phenomenon and prolonged survival of the cultures emphasises the role of urea in the survival of H pylori in acidic environments.

Morphological changes of Campylobacter jejuni growing in liquid culture

Campylobacter jejuni growing in liquid culture was found to exhibit gross morphological changes with time. Exponentially growing cells showed typical short spiral forms. At mid-stationary phase the cells became approximately twice the length of the exponential forms. Late stationary/early decline phase cells were seen to be a mixture of coccal forms and cells which were between 3 and 4 times the length of exponentially growing cells. Continued incubation of cultures eventually resulted in a population largely of coccal forms. These morphological changes have not previously been observed when Camp. jejuni has been grown on agar-based solid medium. It is likely that such changes result from the differential expression of genes that control the timing of cell division.

Structural studies of peptidoglycans in Campylobacter species

Peptidoglycans (PG) from Campylobacter coli, Campylobacter jejuni, and Campylobacter fetus were composed of muramic acid, glucosamine, alanine, glutamic acid, and diaminopimelic acid in a molar ratio of 1.1:1:1.7:1.1:09. Thirty percent of the amino groups of diaminopimelic acid were involved in cross-linkages between peptides. During cultivation, C. coli and C. jejuni changed from a spiral to a coccoid form. In C. coli, we could isolate PG only from the spiral forms in yields of 0.8-1.2% by dry weight. C. fetus did not change to a coccoid form, and always contained PG. Thus, it is possible that the morphological transformation from the spirals to the coccoid forms of C. coli and C. jejuni is accompanied by, and probably due to, the degradation of PG.

Structural analysis of the lipid A component of Campylobacter jejuni CCUG 10936 (serotype O:2) lipopolysaccharide. Description of a lipid A containing a hybrid backbone of 2-amino-2-deoxy-D-glucose and 2,3-diamino-2,3-dideoxy-D-glucose

The chemical structure of Campylobacter jejuni CCUG 10936 lipid A was elucidated. The hydrophilic backbone of the lipid A was shown to consist of three (1----6)-linked bisphosphorylated hexosamine disaccharides. Neglecting the phosphorylation pattern, a D-glucosamine (2-amino-2-deoxy-D-glucose) disaccharide [beta-D-glucosaminyl-(1----6)-D-glucosamine], a hybrid disaccharide of 2,3-diamino-2,3-dideoxy-D-glucose and D-glucosamine [2,3-diamino-2,3-dideoxy-beta-D-glucopyranosyl-(1----6)-D-glucosamine], and a 2,3-diamino-2,3-dideoxy-D-glucose disaccharide were present in a molar ratio of 1:6:1.2. Although the backbones are bisphosphorylated, heterogeneity exists in the substitution of the polar head groups. Phosphorylethanolamine is alpha-glycosidically bound to the reducing sugar residue of the backbone, though C-1 is also non-stoichiometrically substituted by diphosphorylethanolamine. Position 4' of the non-reducing sugar residue carries an ester-bound phosphate group or is non-stoichiometrically substituted by diphosphorylethanolamine. By methylation analysis it was shown that position 6' is the attachment site for the polysaccharide moiety in lipopolysaccharide. These backbone species carry up to six molecules of ester- and amide-bound fatty acids. Four molecules of (R)-3-hydroxytetradecanoic acid are linked directly to the lipid A backbone (at positions 2, 3, 2', and 3'). Laser desorption mass spectrometry showed that both (R)-3-hydroxytetradecanoic acids linked to the non-reducing sugar unit carry, at their 3-hydroxyl group, either two molecules of hexadecanoic acid or one molecule of tetradecanoic and one of hexadecanoic acid. It also suggested that the (R)-3-(tetradecanoyloxy)-tetradecanoic acid was attached at position 2', whereas (R)-3-(hexadecanoyloxy)-tetradecanoic acid was attached at position 3', or at positions 2' and 3'. Therefore, the occurrence of three backbone disaccharides differing in amino sugar composition and presence of a hybrid disaccharide differentiate the lipid A of this C. jejuni strain from enterobacterial and other lipids A described previously.

Antimicrobial activity of Microgard against food spoilage and pathogenic microorganisms

Microgard, a commercially available fermented milk product containing antimicrobial metabolites, was a potent inhibitor for Gram-negative bacteria such as Pseudomonas, Salmonella, and Yersinia when 1% concentration was incorporated into agar media. Gram-positive Bacillus cereus, Staphylococcus aureus, and Listeria monocytogenes were insensitive to Microgard. Kluyveromyces marxianus, an unidentified black yeast, and Penicillium expansum were partially suppressed, whereas Aspergillus niger and a yogurt spoilage yeast were tolerant to 5% Microgard. Optimum activity of Microgard was at pH 5.3 and below; the concentration that gave complete inhibition depended upon the number of bacteria present as well as the genus tested. Blood agar base reversed the antagonistic activity of Microgard against Pseudomonas putida compared with plate count agar.

Characterization of the morphologic conversion of Helicobacter pylori from bacillary to coccoid forms

Growth studies of Helicobacter pylori were performed involving analysis of the bacterium and its microenvironment, to lend insight into the factors responsible for the morphologic conversion phenomenon. H. pylori converted from bacillary to coccoid forms in broth culture after incubation for 5 days under microaerobic conditions with agitation. This morphologic conversion was paralleled by a dramatic decrease in colony-forming units per milliliter (CFU/ml) and a significant endogenous increase in the pH of the broth culture. In addition, removal of broth cultures from microaerobic conditions after 3 days of incubation resulted in a rapid increase in culture pH, a morphologic conversion, and a concomitant decrease of CFU/ml. These observations suggest an inhibitory effect of basic pH, endogenously produced, on the growth of H. pylori in vitro. Experiments designed to identify the reason for the endogenous increase in culture pH demonstrated that the urease enzyme of H. pylori is not primarily responsible for this phenomenon. Rather, H. pylori appears to produce a deaminase enzyme that is likely responsible for the generation of ammonia, which results in the increase in culture pH, the morphologic conversion, and the loss of culturability observed in vitro. Also indicated is the need for a buffering component (for example, bicarbonate) to maintain pH conditions favorable to the growth of H. pylori.